s the ilium.

B. The external iliac artery, cut across.

C. The upper part of the rectum.

D. The ascending pubic ramus.

E. The spine of the ischium, cut.

F. The horizontal pubic ramus, cut.

G. The summit of the bladder covered by the peritonaeum; G *, its side,
not covered by the membrane.

H H. The recto-vesical peritonaeal pouch,

I. The vas deferens.

K. The ureter.

L. The vesicula seminalis.

M, N, O, P, Q, R, S, T, U, refer to the same parts as in Plate 48.

V. The prostate.

W. The lower part of the rectum.

X. The deep perinaeal fascia.

[Illustration: Abdomen, showing bone, blood vessels
and other internal organs.]
Plate 49

COMMENTARY ON PLATES 50 & 51.

THE SURGICAL DISSECTION OF THE SUPERFICIAL STRUCTURES OF THE
MALE PERINAEUM.

The median line of the body is marked as the situation where the
opposite halves unite and constitute a perfect symmetrical figure. Every
structure--superficial as well as deep--which occupies the median line
is either single, by the union of halves, or dual, by the cleavage and
partition of halves. The two sides of the body being absolutely similar,
the median line at which they unite is therefore common to both. Union
along the median line is an occlusion taking place by the junction of
sides; and every hiatus or opening, whether normal or abnormal, which
happens at this line, signifies an omission in the process of central
union. The sexual peculiarities are the results of the operation of this
law, and all forms which are anomalous to either sex, may be interpreted
as gradations in the same process of development; a few of these latter
occasionally come under the notice of the surgeon.

The region which extends from the umbilicus to the point of the coccyx
is marked upon the cutaneous surface by a central raphe dividing the
hypogastrium, the penis, the scrotum, and the perinaeum respectively
into equal and similar sides. The umbilicus is a cicatrix formed after
the metamorphosis of a median foetal structure--the placental cord, &c.
In the normal form, the meatus urinarius and the anus coincide with the
line of the median raphe, and signify omissions at stated intervals
along the line of central union. When between these intervals the
process of union happens likewise to be arrested, malformations are the
result; and of these the following are examples:--Extrusion of the
bladder at the hypogastrium is caused by a congenital hiatus at the
lo